1. Field of the Invention
The present invention relates to an image capturing apparatus which captures an image of an object.
2. Description of the Related Art
In recent years, as image capturing apparatuses such as digital cameras, an image capturing apparatus which has a function of capturing a moving image in addition to a function of capturing a still image, and an image capturing apparatus which has a function of recording sound simultaneously with capturing of a still image or moving image have been developed.
Such image capturing apparatus comprises an image capturing element including the number of pixels required to capture a still image having a resolution higher than that of a moving image. A moving image is captured at a high frame rate and using the number of pixels suited to the moving image as a result of execution of pixel additions, decimations, and the like on the image capturing element. In this way, the image capturing apparatus has a still image drive mode that outputs an image captured by the image capturing element intact (to be referred to as a “still image mode” hereinafter), and a moving image drive mode that executes pixel additions, decimations, and the like (to be referred to as a “moving image mode” hereinafter).
As a technique for capturing a still image during capturing of a moving image, Japanese Patent Laid-Open No. 2006-101473 has proposed a technique that captures an image while switching the drive mode of the image capturing element to the moving image mode or still image mode in accordance with an image to be captured (moving image or still image).
A technique that generates a high-resolution image by compositing a plurality of low-resolution images (to be referred to as “super-resolution” or “super-resolution processing” hereinafter) has been proposed. By applying such super-resolution processing, a still image can be captured during capturing of a moving image. For example, as a technique associated with super-resolution, Japanese Patent Laid-Open No. 2007-19641 has proposed an image signal processing method which executes signal processing after or during execution of the super-resolution processing.
However, when the drive mode of the image capturing element is switched to the still image mode upon capturing a still image during capturing of a moving image, image capturing at a frame rate required to capture a moving image can no longer be realized. Therefore, during capturing of a still image, an immediately preceding frame has to be maintained or a substitute frame such as a full black frame has to be used instead. As a result, a problem is posed, i.e., a moving image is frozen in practice.
Upon application of the super-resolution processing, a moving image can be avoided from being frozen. However, signal processing has to be applied to both low-resolution images for a moving image, and a high-resolution image that has undergone the super-resolution processing. Therefore, a signal processing unit which executes various kinds of processing including synchronization processing, APC correction processing, and the like needs to be configured to time-divisionally process low- and high-resolution images (i.e., to attain a high-speed operation), or such units need to be individually provided in correspondence with various kinds of processing, resulting in an increase in cost.
Furthermore, when super-resolution processing is applied to images for a moving image that have undergone signal processing, APC correction components applied for a moving image appear as unnatural bleeding as a result of the super-resolution processing. For example, upon execution of the APC correction processing, edge emphasized components are mixed. Therefore, when the super-resolution processing is applied to an image mixed with the edge emphasized components, the edge emphasized components spread, thus generating unnatural dark and bright parts in edge parts of a high-resolution image generated by the super-resolution processing.